SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b17df87f8ac13e89469222070732cc0e38096f720ec7e14f449ff41651af510' 
  AND token = 'kmXziqf9ws4d4+4mX5YkJ4nGIWBwuGi5VUgFTC53YVI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}